Hard transparent coatings for the automotive sector come at high premium. They are expensive to produce and have to endure the most demanding of abrasive environments. The substrate glass is hard and has high abrasion resistance but is not the easiest of material to form. It demands a temperature of 700 to 800 Celsius and is of high density.

So TWI's newly developed Vitolane coating for softer substrates looks likely to have a promising future.

'Transparent plastics such as polycarbonate are ideal because they are formed at 130 to140 Celsius' says TWI's ceramics expert Alan Taylor. 'That gives the designer a lot more freedom, as we see in the way headlamps and light clusters have changed design in the last 10-15 years'.

The disadvantage of some such materials is that they are easily scratched unless protected. They turn yellow under ultra violet light and need to be protected in a number of ways.

'The project we got involved with demanded developing a new coating to improve abrasion resistance on softer substrates' says Taylor. The work was part of a multi enterprise collaboration including other members of a consortium with polycarbonate forming capabilities, and the ability to injection mould. They also had a novel technology whereby they put an acrylic film on top of the polycarbonate'.

It was important for two reasons. It provided some UV protection to the underlying polycarbonate but also affected the impact resistance of the polycarbonate.

'We tried our hard coat known as Vitolane and ours out-performed commercially available material. That's how we got involved' recalls Taylor. 'It was then up to us to create a demonstrator which could be field trialled. The industrial trials were undertaken and shown to be highly successful. We now have a coating that technically worked well by the end of the project.'

TWI had come up with a hard transparent coating for demonstrator samples that had a very good abrasion performance and that also passed the UV test.